1. Field of the Invention
This invention relates to automatic toll ticketing subsystems for use in communication switching systems, and more particularly, to an addressable scanner for monitoring usage times for originating junctors and trunk circuits of a communication switching system.
2. Description of the Prior Art.
Communication switching systems, such as telephone switching systems, generally employ toll ticketing subsystems for the purpose of billing customers for usage of telephone facilities. The essential functions of the toll ticketing subsystem are to collect, format, and record toll utilization data for future processing. The data gathered and reported is used for customer billing, toll separation, traffic engineering studies, planning and evaluation of toll services, and maintenance of toll facilities.
Automatic toll ticketing equipment may be employed to handle message rate service local traffic MRS and direct distance dialed toll traffic DDD, for example. Customers who subscribe to message rate service are allowed to place a limited number of calls of unlimited duration to points within a predefined geographic zone. For calls of this type, the ticketing subsystem monitors the status of originating junctors or incoming PABX trunks. When an answer condition is detected, the call is pegged as a completed call.
The ticketing subystem may also collect customer billing data for direct distance dialed toll traffic. All direct distance dialed calls are ticketed as timed calls by monitoring the status of outgoing trunk circuits for both answer and disconnect times, so that the total conversation time can be determined at an accounting center.
The originating junctors and trunk circuits include supervisory hold and answer relays which in turn operate slave relays the contacts of which provide scan points which permit monitoring of the completed call for message rate service and an indication of answer and disconnect times for direct distance dialed calls. The toll ticketing subsystem includes a scanner which serves to scan the condition of the scan points.
Certain known toll ticketing systems employ scanning devices of the rotary type where scanning of a plurality of scan points is initiated at one of the scan points and the remaining scan points are scanned sequentially until end of scan is reached, at which point the scanner resets to the start position. Thus, in such systems, it is necessary to scan all of the scan points even though only certain ones of the scan points are associated with busy trunk circuits or originating junctor circuits. The scanner provides output data indicative of the condition of all of the scan points and thus the busy conditions for all of the trunk circuits and originating junctor circuits.
In common control systems, the automatic toll ticketing equipment may be controlled by the common control equipment to initiate the scanning of the scan points and the data provided as a result of such scan is returned to the common control equipment. However, since the known systems it is common to scan all of the scan points, the common control apparatus must allot time to the automatic toll ticketing equipment to initiate scanning and to recover and process the data resulting from the scan. In telephone switching systems which include a large number of originating junctors and trunk circuits, the need to scan all of the originating junctors and trunk circuits results in appreciable time loss for the common control apparatus.
Accordingly, it would be desirable to have an automatic toll ticketing apparatus which is controllable by common control apparatus in a communication switching system, which has the capability of scanning a particular group of scan points which is known to include at least one scanning device associated with a busy originating junctor or trunk circuit.